1. Field of the Invention
The present invention relates to a compressor, and, more particularly, to a compressor in which moving components are lubricated with a lubricating oil contained in a refrigerant.
2. Description of the Related Art
A variable capacity compressor (hereinafter, referred simply to as a compressor) for use in an automotive air conditioner is known and a typical variable capacity compressor is shown in FIG. 7, for example. That is a housing 101 has a crank chamber 102 formed therein, and a drive shaft 103 is rotatably disposed therein. A lip seal 104 is interposed between the drive shaft 103 and the housing 101 so as to seal off a gap therebetween.
The drive shaft 103 is operatively coupled to an automotive engine Eg as an external drive source via an electromagnetic friction clutch 105 as a power transmission mechanism. The friction clutch 105 comprises a rotor 106 operatively coupled to the automotive engine Eg, an armature 17 fixed to the drive shaft 103 so as to rotate together with the drive shaft 103 and a coil 108. When excited, the coil 108 attracts the armature 107 toward the rotor 106 to fasten the two components together, whereby power can be transmitted between the automotive engine Eg and the drive shaft 103 (the friction clutch 105 is switched on). When the coil 108 is demagnetized in this state, the armature 107 moves away from the rotor 106, whereby power transmission between the automotive engine Eg and the drive shaft 103 is cut off (the friction clutch is switched off).
A rotation support member 109 is fixed to the drive shaft 103 in the crank chamber 102, and a swash plate 110 is coupled to the rotation support unit 109 via a hinge mechanism 111. The swash plate 110 can rotate together with the drive shaft 103 and the inclination angle thereof can be varied relative to the axis L of the drive shaft 103 because it is coupled to the rotation support unit 109 via the hinge mechanism 111. A minimum inclination angle regulating portion 112 is provided on the drive shaft 103 and regulates the minimum inclination angle of the swash plate 110 by abutting thereagainst.
The cylinder bore 113, a suction chamber 114 and a discharge chamber 115 are formed in the housing 101. A piston 116 is reciprocally accommodated in the cylinder bore 113 and is coupled to the swash plate 110.
The rotating motion of the drive shaft 103 is converted into reciprocating motion of the piston 116 via the rotation support unit 109, the hinge mechanism 111 and the swash plate 110, whereby a compression cycle is repeated which is made up of suction step of sucking the refrigerant gas from the suction chamber 114 into the cylinder bore 113 via a suction port 117a and a suction valve 117b of a valve/port forming unit 117 provided in the housing 102, a compression step of compressing the sucked refrigerant gas and discharge step of discharging the compressed refrigerant gas to the discharge chamber 115 via a discharge port 117c and a discharge valve 117d of the valve/port forming unit 117.
The suction chamber 114 and the discharge chamber 115 are connected to each other via an external refrigerant circuit, not shown. Refrigerant discharged from the discharge chamber 115 is introduced into the external refrigerant circuit. Heat exchange is carried out in this external refrigerant circuit using the refrigerant. Refrigerant discharged from the external refrigerant circuit is introduced into the suction chamber 114 and is then sucked into the cylinder bore 113 for re-compression.
A gas bleed passage 119 communicates with the crank chamber 102 and the suction chamber 114. A gas supply passage 120 communicates with the discharge chamber 115 and the crank chamber 102. A control valve 121 is disposed in the gas supply passage 120 for regulating the opening degree of the gas supply passage 120.
The control valve 121 is constructed to be driven by an electric current outputted by a drive circuit, not shown, based on a signal from a control computer, not shown, so as to regulate the opening degree of the gas supply passage 120. In the state in which it is not activated by the drive circuit, the control valve 121 operates so as to open the gas supply passage 120, whereas in the state in which it is activated, the control valve 121 operates so as to regulate the opening degree of the gas supply passage 120.
The balance between the amount of the high pressure gas introduced into the crank chamber 102 via the gas supply passage 120 and the amount of the gas flowing out from the crank chamber 102 via the gas bleed passage 119 is controlled by regulating the opening degree of the control valve 121 to thereby determine a crank pressure Pc. A difference between the crank pressure Pc and the internal pressure in the cylinder bore 113 on the opposite side of the piston is varied in response to a variation in the crank pressure Pc and, as a result of a variation in the inclination angle of the swash plate 110, the stroke or the discharge capacity of the piston is regulated.
If, for example, the friction clutch 105 is switched off in response to switching off an air conditioner switch, not shown, from the state in which the compressor is running at the maximum discharge capacity thereof or that the automotive engine Eg is halted, whereby the operation of the compressor is also stopped, activation of the control valve 121 is also stopped (the input current value is zero), and it follows that the gas supply passage 120 is fully opened in a sudden fashion. Consequently, the supply volume of high pressure refrigerant gas from the discharge chamber 115 to the crank chamber 102 is increased suddenly, and since the gas bleed passage 119 cannot bleed the suddenly increased volume of refrigerant gas, the pressure inside the crank chamber 102 is increased excessively. In addition, the pressure inside the cylinder bore 113 is reduced because the pressure tends to become uniform to a lower pressure in the suction chamber 114 due to the stopping of the operation of the compressor. As a result, the difference in pressure between the cylinder bore 113 and the crank chamber 102 is increased excessively.
Due to this, the stash plate 110 inclination angle is set to the minimum inclination angle (shown by chain double-dashed lines in FIG. 7) and it is pressed against the minimum inclination angle regulating portion 112 with an excessively large force and strongly pulls the rotation support unit 109 rearward (rightward as viewed in the figure) via the hinge mechanism 111. As a result, the drive shaft 103 is subjected to a strong moving force acting rearward along the axis L thereof and is forced to slide against the biasing force of a drive shaft biasing spring 118. Due to this, the following problems may be caused.
(a) When the drive shaft 103 slides in the axial L direction, there is a possibility that the sliding position of the lip seal 104 will deviate from a predetermined position called a contact line. There are many cases where foreign matter such as sludge adheres to portions deviating from the contact line on the outer circumferential surface of the drive shaft 103. Due to this, sludge bites into the lip seal 104 and the drive shaft 103 and this reduces the shaft seal performance, whereby a defect such as gas leakage occurs.
(b) When the friction clutch is switched off, in other words, power transmission between the automotive engine Eg and the drive shaft 103 is cut off and, if the drive shaft 103 slides rearward in the axial L direction, the armature 107 fixed to the drive shaft 103 moves toward the rotor 106. A clearance between the rotor 106 and the armature 107 is very small (for example, 0.5 mm) in the state in which the friction clutch 105 is switched off. Consequently, the rearward sliding of the drive shaft 113 along the axial L direction thereof easily eliminates the clearance set between the rotor 106 and the armature 107 and this permits the armature 107 to be brought into sliding contact with the rotating rotor 106, generating abnormal noise and vibrations. Furthermore, a power transmission is permitted to a certain extent.
(c) when the drive shaft 103 slides rearward in the axial L direction thereof, the piston 116 coupled to this drive shaft 103 via the swash plate 110 slides rearward in the cylinder bore 113 and the dead center thereof may deviate toward the valve/port forming unit 117. In addition, the drive shaft 103 continues to rotate for a certain period of time due to inertia immediately after the friction clutch 105 is switched off or the automotive engine Eg is stopped. Consequently, while the driveshaft 103 rotates under inertia, the piston 116 impacts against the valve/port forming unit 117 when it shifts to the top dead center thereof, and this impact causes vibrations and noise.
Note that, to prevent the drive shaft 103 from sliding, it is possible to increase the biasing force of the drive shaft biasing spring 118 as a countermeasure, but this in turn causes new problems in that the durability of a thrust bearing for carrying a great load is deteriorated and that the power loss is increased.
In the aforesaid compressor, to obtain smooth movements of moving components therein, the respective moving components need to be lubricated. To make this happen, in the compressor, a mist of lubricating oil is mixed in the refrigerant so that a mist of lubricating oil is circulated together with refrigerant when the refrigerant circulates between the compressor and the external refrigerant circuit. In the compressor, the moving components are designed to be exposed to the refrigerant, and therefore, the moving components are also exposed to the mist of lubricating oil, this allowing the lubrication of the moving components.
However, the mist of lubricating oil introduced into the external refrigerant circuit in conjunction with the circulation of the refrigerant reduces the efficiency of heat exchange that is to be carried out in the external refrigerant circuit. Moreover, this also means that the lubricating oil is discharged out of the interior of the compressor to the outside thereof, and the volume of lubricating oil inside the compressor is reduced, this deteriorating the lubricating efficiency inside the compressor.
The respective problems caused in association with the increase in pressure in the crank chamber 102 can be solved by the constitution disclosed in Japanese Unexamined Patent Publication (Kokai) No. 11-315785. In this constitution, a check valve for regulating the refrigerant flow direction is provided between the discharge chamber and the external refrigerant circuit, whereby a reverse flow from the external refrigerant circuit to the discharge chamber is prevented. Thus, preventing the reverse flow of refrigerant eliminates a risk of high pressure refrigerant existing on the external refrigerant circuit side being introduced into the crank chamber 102 via a gas supply passage 120 in an aforesaid state in which the gas supply passage 120 is fully opened. This, in turn, eliminates a risk of an internal pressure inside the crank chamber 102 being increased excessively.
In addition, the problem caused by the discharge of lubricating oil to the external refrigerant circuit can be solved by a constitution disclosed, for example, in Japanese Unexamined Patent Publication (Kokai) No. 10-281060. In this constitution, an oil separator is provided in a discharge chamber for separating atomized lubricating oil mixed with refrigerant from the refrigerant so as to prevent the lubricating oil from being discharged to an external refrigerant circuit.
In the former disclosure, however, only the prevention of the reverse flow of refrigerant is dealt with, and no consideration is taken into for the problem of the discharge of lubricating oil into the external refrigerant circuit. Additionally, in contrast to the former disclosure, in the latter disclosure, only the problem of the discharge of lubricating oil into the external refrigerant circuit is dealt with, and no consideration is taken for the problem of the increase in pressure in the crank chamber.
An object of the present invention is to provide a compressor which can prevent not only the reverse flow of refrigerant from an external refrigerant circuit to a discharge chamber but also the discharge of lubricating oil into the external refrigerant circuit.
To solve the above described problems, the present invention provides a compressor comprising: a housing having a compression chamber, a discharge chamber, and a suction chamber, a refrigerant being sucked from the suction chamber into the compression chamber and discharged from compression chamber into the discharge chamber; a movable member to compress the refrigerant in the compression chamber; a discharge passage connecting the discharge chamber to an external refrigerant circuit; and a suction passage connecting the suction chamber to the external refrigerant circuit; wherein a check valve preventing reverse flow of the refrigerant from the external refrigerant circuit to the discharge chamber, an oil separator separating a mist of lubricating oil contained in the refrigerant from the refrigerant, and an oil passage introducing the separated lubricating oil into a low pressure region in the compressor, are provided in the discharge chamber or the discharge passage.
According to this arrangement, the oil separator separates the refrigerant from the lubricating oil to thereby prevent the lubricating oil from being discharged into the external refrigerant circuit. Since the lubricating oil causes deterioration in heat exchange efficiency in the external refrigerant circuit, the separation can suppress the reduction in the heat exchange efficiency. The lubricating oil separated from the refrigerant is introduced into the low pressure region via the oil supply passage. Preferably, the low pressure region may be the suction chamber, the suction passage, or the crank chamber formed in the housing. This not only prevents the reduction in the amount of the lubricating oil in the compressor including the suction passage but also enables the proper lubrication of the interior of the compressor. In addition, the check valve prevents the reverse flow of the refrigerant from the external refrigerant circuit to the discharge chamber.
Preferably, the oil separator is disposed upstream of the check valve. The oil passage for introducing the lubricating oil separated by the oil separator into the low pressurized region is disposed upstream of the check valve together with the oil separator. That is, even if the downstream side of the check valve is subjected to a higher pressure than the upstream side thereof, there is no risk of the refrigerant existing on the downstream side flowing to the upstream side via the oil passage. Consequently, the reverse flow of refrigerant can be prevented without providing a closing means for closing the oil passage along the same passage.
Preferably, the check valve and the oil separator are integrally arranged as a unit. In this arrangement, a space for installation of the relevant components can be reduced and the fabricating properties can be improved, compared with a construction in which a check valve and an, oil separator are provided separately.
Preferably, the unit comprises a case to which the check valve is attached, the case having a substantially cylindrical portion having an inlet opening for introducing the refrigerant into the case such that the refrigerant turns about an axis of the case, the case also having an outlet for the refrigerant which passes through the check valve after the refrigerant is separated from the lubricating oil, and an outlet for the discharge lubricating oil which is separated from the refrigerant. Preferably, the refrigerant turns in the circumferential gap between an outer circumferential surface of the check valve and an inner surface of the case. In this arrangement, the refrigerant reverse flow preventing function and the lubricating oil separating function carried out by the unit are realized by the case and the check valve accommodated in the case. The mist of lubricating oil mixed in the refrigerant gas introduced into the case is centrifugally separated from the refrigerant while turning inside the case. The refrigerant from which the lubricating oil is separated is introduced into the check valve to be discharged to the external refrigerant circuit side.
Preferably,the check valve comprises a valve casing having a valve seat, a valve element arranged in the valve casing, and an urging member resiliently urging the valve element toward the valve seat, the valve casing being attached to the casing. Preferably, the valve element has an outer circumferential surface and at least one groove axially extending in the outer circumferential surface.
Preferably, the compressor is a variable capacity compressor comprising a crank chamber formed in the housing, a drive shaft rotatably supported in the crank chamber, a swash plate driven for rotation by the drive shaft and supported by the drive shaft so that an inclination angle thereof relative to the drive shaft changes, a piston as the movable member operatively coupled to the swash plate, a cylinder bore for reciprocally accommodating therein the piston and in which the compression chamber is formed by the piston, a gas bleed passage for providing a communication between the suction chamber and the crank chamber, and a control valve for controlling a pressure in the crank chamber so as to vary the stroke of the piston. In this arrangement, in the event that the amount of the circulating refrigerant is reduced, the check valve cuts off the passage of refrigerant between the discharge chamber and the external refrigerant circuit, whereby the flow of the refrigerant to the external refrigerant circuit is suppressed.
Preferably, the low pressure region is the crank chamber, and the lubricating oil separated by the oil separator is supplied to the crank chamber via the oil passage. In this arrangement, the lubricating efficiency of the sliding components of the mechanism in the crank chamber is improved. Since there exist in the crank chamber a relatively large number of sliding components of the mechanism for converting the rotating motion of the drive shaft into the reciprocal motion of the piston, the improvement in the lubricating efficiency of those sliding components is useful in improving the operation efficiency of the compressor.
Preferably, the control valve regulates the opening degree of the oil passage so as to supply lubricating oil separated by the oil separator to the crank chamber and varies the pressure in the crank chamber so as to vary the stroke of the piston. In this arrangement, the lubricating oil can be supplied to the crank chamber during the small capacity operation in which the amount of the circulating refrigerant, as well as the amount of leaking refrigerant from the compression chamber to the crank chamber via the gap between the cylinder bore and the piston is reduced. In addition, since the passage, through which the refrigerant is allowed to pass for varying the pressure in the crank chamber, can be shared as the oil passage, the construction of the compressor can be simplified.